The fact that we had no idea what you were referring to probably says something.
In my local forest, I'm thankful for random stickers on signs. They're a lot easier to deal with than spray paint and other kinds of vandalism, so maybe you should count your blessings and knock on wood for first-world problems. Most are not difficult to remove. A paint scraper or classic box cutter in scraper mode are tools for the job. Sometimes I just paint over them.
Cheers...